Tag Archives: Mountain bike

Last week, while getting ready to climb a steep section of my route home, I vigorously shifted into my lowest gear while riding my 1987 Panasonic MC 7500 winter bike. That resulted in my chain over-shifting and falling into the spokes. Uh oh! It took about 15 minutes for me to dislodge the chain and ride home, after turning the bike upside down for diagnosis and repair. I had to remove my Paul’s chain keeper in order move the chain, as it had gotten wedged between the chain keeper and chain ring. Still, I wasn’t worried because I stopped the bike the minute this occurred, and didn’t expect that I had done much damage.

I had built this wheelset about a year and a half ago using Quando cartridge bearing hubs, laced to SunRims CR18 rims. For the few weeks preceding this mishap, I had been hearing a clunking noise in the rear of the bike, occurring while pedaling and coasting, but louder when riding at speed. It took a while for me to clue in to what the noise might mean. At first, I thought it was the saddle rails or seat post, because I only heard it when working hard at accelerating. But then I began hearing it while coasting. Then I thought it was the replacement freewheel I was using – perhaps the freewheel cover plate was coming loose and the body was clunking around. Bicycle noises can be maddening to diagnose!

Spoke damage.

When I finally had time to get the bike into the shop stand, I was saddened to see that the chain had damaged all the drive side spokes in my little mishap. Doh! Good thing I checked. So, I proceeded to disassemble the wheel, all the while wondering whether I had the right length replacement spokes (that’s why you always buy extras…), and questioning whether I was up to a wheel building experience on this nice sunny afternoon.

Once I had the spokes out, which I removed very slowly and methodically (spokes under tension are dangerous projectiles), I examined the hub body. It looked pretty good. Okay, let’s build the wheel again with some new spokes. Fortunately, I had 9 spokes on hand of the exact length needed. In a sort of thoughtless way I began turning the hub axle, perhaps in an attempt to delay the inevitable. That’s when I heard a strange grinding/clicking sound. I held the hub close to my ears to listen further. Finally, the sound stopped, but was replaced by a very tight spot when turning the axle of the hub. Very tight. Not normal! The source of the clunking was now illuminated. But, what to do?

I could attempt to diagnose the cartridge bearings, or I could try to find the right rear hub with 126mm rear spacing (mission impossible?). The latter turned out to be the best course of action. Velo Orange sells a 126mm rear hubwith freewheel threads and 36 holes – just what I needed. Mission accomplished.

Meanwhile, I removed the dust covers on the Quando hubs. Perhaps with this winter’s especially rainy and muddy rides, bad stuff had made its way into the cartridge bearings and could be simply cleaned out.

No such luck. The bearing grease (which has been removed in the above photos), was pristine. Undaunted, I decided to clean the bearings and re-grease them, to see if by some chance that would change the hub’s tight spot (which was illogical of course).

The bearings on these Quando hubs are either bad, or not properly adjusted, or the races and cups in the hubs are damaged. Cartridge bearings do not work in the same way as cup and cone style bearings. The latter’s adjustment is achieved by the correct position of the cone against the cup, something most experienced mechanics can do easily.

Cartridge bearings are engineered differently. The preload adjustment is done by the factory when the bearings are pressed into the hub. If it is wrong, correcting it can be a problem. A cartridge bearing hub’s races can also be damaged by improper installation (or removal).

While it may be possible to have these hubs diagnosed and repaired by a mechanic with the right equipment, the cost to do so is not justified here (throwaway technology strikes again). Now, I will try to look forward to rebuilding the rear wheel with my new VO hub, when it arrives. The front hub spins just fine and has no issues, for now. But, given this experience, I will plan to monitor it in the future.

These are the words I say to myself when I am riding especially fast. Or especially slowly, as of late.

This winter I have been using my Panasonic MC 7500 winter bike as my primary commuter, which is a change from past winters, partly driven by this winter’s wet and colder conditions which heralded the onset of a typically Portland rainy season last November. Very recent winters have been gloriously warm and dry, so my choice of commuting vehicles was vastly expanded and even included scooter rides in the dead of December. But, not this winter. Portland is back to typical seasonal weather which can include anything from 35 degrees and raining hard, to light sprinkles in the lower 50’s (like today), and the occasional freezing rain and snow. The short days also come with twilight seeming to descend in apocalyptic fashion in the middle of the afternoon.

This bike was actually quite the machine in its day – the top of the line Mountain Bike in Panasonic’s line up in 1987. It is built with Tange Prestige Cro-Mo double butted tubes, with forged drop outs and chromed chain stays. The geometry on the smaller frame that I am riding features a slack 70 degree head tube combined with minimal fork rake, which would normally make it less than ideal for commuting, but its long wheelbase (107 cm) makes up for the higher than ideal wheel flop. Consequently, I can usually avoid putting my foot down as I approach red lights and four way stops.

I bought this Panasonic as a frame and fork, then built it into a city commuter. It went through various iterations, and now is set up for maximum comfort and utility.

I was using a Shimano grip shifter and a 6 speed cassette, but after a black ice crash in 2012, the shifter broke apart (because it is made of plastic), so I splurged on a $7 no name friction shifter, made of good old steel. That meant that I could install a 7 speed freewheel, and increase the bike’s gear range a bit.

I had been using these UNO city bars, pictured above, but the shape and width did not agree with my anatomy, so I swapped them out for a vintage steel Northroad bar. This bar is a great improvement in comfort, being narrower and putting my hands and shoulders in a much more neutral position, and increases the bike’s un-coolness factor by a few thousand degrees.

Steel Northroad bars

Further agitating bike snobs in Pdx, the Panasonic is sporting a duct tape rear fender repair job, and a ghastly kickstand.

The kickstand is a convenient accessory, and this design is useful for any bike where mounting in back of the bottom bracket is not an option (in this case due to the U-brakes residing there). The stand is adjustable to any wheel size, and keeps the bike secure, even when I have my bags loaded up with groceries.

I like using these Jandd Hurricane bags, which are aptly named and can handle just about any kind of weather. Their vibrant colors augment my winter bike’s 1980’s color scheme, and add a lot to its visibility. If you haven’t used Jandd bags, you are missing out on the ultimate in practicality and quality. I have a set of Jandd panniers that are 30 years old, and still look new.

The Panasonic MC 7500 is a bike that enthusiasts have embraced, but the frame does have its downsides – one of them being that on some builds, holes drilled in the seat stays (necessary to allow heat to escape while brazing), were actually drilled very close to the seat stay attachment. Fortunately, on my frame, the holes have been drilled near the dropouts. Unfortunately, the seat stay holes have caused a stress riser to appear on this cyclist’s bike.

Specialized Nimbus Tires. Never a flat in six years, and the exact opposite of supple side walls.

Possible stress crack

After sanding to remove the paint, no stress crack visible.

On my own frame, I had concerns about the paint cracks which had developed near to the U-Brake braze-ons on the chain stays. Whenever you heat the tubes to braze, there is a danger of overheating and weakening them. Since the frame was already cosmetically challenged, I had no qualms about taking my emery cloth and sandpaper to this area to see what lay beneath the cracked paint. Fortunately, nothing at all. But now I can monitor this area. I will paint it with Testor’s clear paint so that I can watch for any future changes.

SunRims on the wheelset I built for this bike – holding up okay but the sidewalls have been scored by my too hard brake pads.

Offending hard pad on the U Brake – showing no wear which is a bad sign. Meaning that my rims have suffered instead.

Repair job on the broken fender attachment.

Repaired fender bracket.

While I had the bike in the shop stand, I decided to do a full tune-up. I washed the wheels (a new wheelset which I built last year, and which are working well), picked rim material out of the brake pads, sanded the rear ones, replaced the too hard original Tektro pads which had messed up my new rims, and cleaned and lubricated the SunTour freewheel (more on that, below). I repaired the broken fender attachment by rummaging through the parts bin to find a reasonable facsimile with which to repair the broken bracket. I drilled a new hole through the center of the fender, and installed the new bracket. Hopefully, it will survive and thrive.

New front Kool Stop pads – replacing the original Tektros which badly scored my new rims.

But now, to my chagrin, my newly cleaned and lubricated 7 speed Suntour freewheel is making very odd grinding and clunking sounds. I have always loved Suntour freewheels, and have never had one fail on me. After doing some research,Sheldon Brown (RIP) came to the rescue. He described a situation similar to mine, where my newly lubricated freewheel began sounding clunky under load, and noisy while freewheeling. I believe the problem may be a loose cover plate. Meanwhile, I have a fun old Atom 5 speed freewheel from the 1970’s with English threads which I am going to install while I troubleshoot the beloved Suntour. The higher geared old Atom freewheel should make me ride even more slowly. But, as I said before, it’s not me, it’s the bike.